Abstract In the 1960s and 70s, great interest developed in the thorium fuel cycle as a supplement to limited uranium reserves. A great amount of work was carried out and many interesting developments resulted, among which were prototype high temperature reactors. It was shown that thorium could be used practically in any type of existing reactor. These initiatives have been virtually brought to a halt for various reasons, except in India, which has continued with its thorium activities. Recently however, new considerations have revived interest in thorium. An overview of the specificities of the thorium fuel cycle was carried out and the most interesting projects launched in the 1960s are recalled. The new concepts are analyzed briefly and some lines of thought for the future are proposed.